Electrical submersible pumps (ESP) are commonly used to pump fluids from hydrocarbon producing wells. A typical ESP includes a pump, which is often a centrifugal type, driven by an electrical motor. A power cord extends torn a wellhead down the well to the motor for supplying power to the motor. The power cord may have a motor lead on its lower end with an electrical connector that plugs into engagement with an electrical receptacle on the motor. The engagement of the electrical connector and the electrical receptacle must be able to withstand high pressures and temperatures over a period of time that may be years.
One type of electrical receptacle has a base with a central cavity extending into the motor for the location of motor electrical terminals. Threaded holes are located on opposite sides of the cavity. The electrical connector has a housing with a central cavity containing motor lead electrical terminals that stab into engagement with the motor electrical terminals. The housing of the electrical connector has a flange with bolt holes that align with the threaded holes in the base of the electrical receptacle. Bolts insert through the bolt holes and engage the threaded holes to secure the electrical connector to the electrical receptacle.
While this arrangement works well, due to tolerances, some times the bolt holes do not precisely align with the threaded holes. To account for a tolerance stack up, both bolt holes in the flange are made significantly larger than the threaded holes. Alignment shims must be employed to properly align the bolts with the threaded holes. The alignment shims are placed on the back of the electrical connector to centralize the bolts with the threaded holes and accommodate for lateral movement of the connector housing relative to the connector receptacle. During running in of the ESP, the motor may slide against different parts of the well casing, and lateral loads on the electrical connector can result, causing sliding movement of the electrical connector on the receptacle due to the large diameter bolt holes. Shifting of the electrical connector on the receptacle can possibly result in a loss of the sealing engagement.
The alignment shims are comparable in size to a ⅜ inch washer and may be dropped or lost during connection of the motor lead with the motor while the ESP is suspended above a rig floor. Also, the alignment shims may be inadvertently omitted. As a result, the bolts could bottom out in the threaded holes and not transmit the proper preload forces to the electrical connector.